I have a sore near the top of my bottom (closer to the small of my back, but still in that region). I noticed it last night because it was bleeding pretty bad. Hard to really see, but it looks like a sore back there, and it's caked with something (definitely blood, that much is certain). It's sore when I try to lay on my back or sit down on that area, and seems to make it bleed more. What is this? Is it something I need to go to the ER about?